精密外罩的成形工艺及模具

分析了外罩的工艺性能和材料性能,叙述了精密外罩的成形工艺及其模具结构.     

Windows图元文件的应用

采用MFC的单文档框架保存图元文件时,用MFC AppWizard向导产生应用框架,在头文件中增加成员变量、"建立图元文件"、菜单对应的消息处理函数等,经过编译、链接形成可执行文件MyWMF.exe.利用MFC中已经封装好的类CmetaFileDC能实现该图元文件的各种操作.     

所见即所得技术的应用

在程序开发过程中利用VC中所见即所得编程技术,通过设置映射模式,统一输入参数单位,调用坐标转换和字体处理函数,将实际的坐标值和字体转换为基于输出设备对象的逻辑坐标值和字体,由程序实现在不同设备上输出一致的显示结果.该方法也可用于文字处理软件,实现文字编辑的所见即所得.     

Study on BMT Millimeter Wave Dielectric Resonators

The microwave dielectric properties and microstructures of Ba(Mg_1/3Ta_2/3)O₃ (BMT) ceramics were investigated. In order to reduce the evaporation of MgO at high temperature, burying in MgO powders sintered BMT ceramics. The relationship between the composition and Q value of BMT ceramics was discussed. Dielectric resonators using in millimeter wave band have been designed and fabricated. Their attenuations at central resonation frequency (τ_f) are less than 35dB. Temperature coefficients of resonant frequency are adjustable and less than 2 ppm/°C.     

Energy band diagram of a Si metal-oxide-semiconductor field-effect transistor

We have calculated the energy band diagram of a Si metal-oxide-semiconductor field-effect transistor (FET) with two-storied gates most recently experimentally investigated by Matsuoka et al. (see Appl. Phys. Lett., vol. 64, p. 586, 1994). From out numerical calculations of the three-dimensional Hartree-Fock equation, it is found that the increase of the upper gate negative bias does not transform the simple quantum wire (conducting channel created by the lower gate) into coupled quantum dots, it only makes the conducting channel narrower. Without the lower gate, the system can be well approximated by a two-dimensional Laplace equation. By the corresponding analytical solution it is shown that only in the spatial region very close to the upper gate where can we observe very weak quantum barriers induced by individual metal lines in the upper gate. For the FET structure of Matsuoka et al., coupled quantum dots and thus Coulomb blockade effect are not very likely. The experimental results of transconductance and conductance as functions of upper gate and lower gate can be well explained by the carrier transport through the part of the conducting channel compressed by the upper gate. Precaution should therefore be exercised when analysing experimental results concerning small-size and quantum structure systems,.<>     

滨海地区混凝土露筋的危害与防治

露筋是滨海地区常出现的钢筋混凝土构件损害缺陷,持续发展会影响其耐久性和安全性.钢筋在各种环境的抗腐蚀研究课题一直在持续,目前虽然已研究出电化学脱盐、牺牲阳极保护、外加电流阴极保护等几种方法来保护钢筋;但主要针对的是已出现钢筋锈蚀的抑制和抵消措施,在滨海地区持续盐雾的不良环境中的预防保护还不够重视.明晰钢筋在钢筋混凝土复...     

Optimal preventive maintenance scheduling in semiconductor manufacturing

Preventive maintenance (PM) scheduling is a very challenging task in semiconductor manufacturing due to the complexity of highly integrated fab tools and systems, the interdependence between PM tasks, and the balancing of work-in-process (WIP) with demand/throughput requirements. In this paper, we propose a two-level hierarchical modeling framework. At the higher level is a model for long-term planning, and at the lower level is a model for short-term PM scheduling. Solving the lower level problem is the focus of this paper. We develop mixed-integer programming (MIP) models for scheduling all due PM tasks for a group of tools, over a planning horizon. Interdependence among different PM tasks, production planning data such as projected WIP levels, manpower constraints, and associated PM time windows and costs, are incorporated in the model. Results of a simulation study comparing the performance of the model-based PM schedule with that of a baseline reference schedule are also presented.     

保密传真通信系统的仿真实现

实际的保密传真通信系统是一个功能结构复杂的系统。在建立新系统前,通常需要对系统进行建模和仿真以消除系统中潜在的瓶颈,提高系统成功的概率。文中在分析了保密传真通信系统的工作原理之后,对保密传真通信系统的信源编码模块、加解密模块和调制解调模块进行了Matlab仿真实现,仿真结果达到了预期目标。     

NON-PARAMETRIC TOPIC MODEL FOR DISCOVERING GEOGRAPHICAL TOPIC VARIATIONS

This paper presents a non-parametric topic model that captures not only the latent topics in text collections, but also how the topics change over space. Unlike other recent work that relies on either Gaussian assumptions or diseretization of locations, here topics are associated with a distance dependent Chinese Restaurant Process （ddCRP）, and for each document, the observed words are influenced by the document＇s GPS-tag. Our model allows both unbound number and flexible distribution of the geographical variations of the topics＇ content. We develop a Gibbs sampler for the proposal, and compare it with existing models on a real data set basis.     

Thermal stability investigations of AlGaN/GaN HEMTs with various high work function gate metal designs

The operation of high power RF transistor generates a huge amount of heat and thermal effect is a major consideration for improving the efficiency of power transistors. AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrates have been studied extensively because of their high thermal conductivity. This study comprehensively investigates the DC, low frequency noise, microwave and RF power performance of Al_0.27Ga_0.73N/GaN HEMTs on silicon substrates at temperatures from room temperature to 100 °C using high work function metals such as palladium (Pd) and iridium (Ir) gate metals. Although the conventional Ni gate exhibited a good metal work function with AlGaN, which is beneficial for increasing the Schottky barrier height of HEMTs, the diffusion of Ni metal toward the AlGaN and GaN layers influences the DC and RF stability of the device at high temperatures or over long-term operation. Pd and Ir exhibited less diffusion at high temperature than Ni, resulting in less degradation of device characteristics after high temperature operation.